The present invention relates to an orbital disk grinder.
More particularly, it relates to an orbital disk grinder which has a housing accommodating a motor which moves a grinding disk via an output shaft while gyrating in a circular orbit and simultaneously rotating about its axis.
Orbital disk grinders of the generic type have been freely available on the market for many years. If they are lifted off the workpiece with the motor still running, these grinders have the disadvantage that in the fine processing stage i.e. whilst the grinding disk rotates about its axis, simply due to the bearing friction, at approx. 200 min.sup.-1, resulting from the friction between the output shaft and the eccentric journal, the grinding plate accelerates to the idling speed of the output shaft, which is up to 13,000 r.p.m. This speed increase can result in so much material being removed when the grinding disk is applied to the workpiece, that irreparable damage to the workpiece surface occurs.
A further development of the orbital disk grinder of this type, in accordance with EP-PS 320 599, features an electromagnetic brake located between the grinding plate and the orbital disk grinder housing, which is intended to prevent a speed increase in the grinding disk. This electromagnetic brake is very effective, but has the disadvantage that additional braking energy is required in order to compensate for the acceleration energy. This results in wasted energy. Furthermore, greater design requirements are involved for the electromagnetic braking device, with the mass and volume of the orbital disk grinder increasing considerably.
From U.S. Pat. No. A 5,018,314, an orbital disk grinder is known which, based on the orbital disk grinder of this type, is intended to prevent the acceleration of the grinding disk by mechanical means. In this case too, the acceleration energy is "destroyed".